1. Technical Field
The present invention relates to a surface acoustic wave device, a transmitter, and a transceiver.
2. Related Art
As disclosed in JP-A-1-252016, a surface acoustic wave element SD100 shown in FIG. 20A is a surface acoustic wave element in related art. The surface acoustic wave element SD100 includes a piezoelectric substrate SB100 having a first interdigital transducer CE101 and a second interdigital transducer CE102 as a pair, a third interdigital transducer CE103 and a fourth interdigital transducer CE104 as a pair corresponding to the first interdigital transducer CE101 and the second interdigital transducer CE102, and a first reflector RF101 and a second reflector RF102 as a pair formed in a position to sandwich the first interdigital transducer CE101 through the fourth interdigital transducer CE104 thereon.
Now, usage of the surface acoustic wave element SD100 having a configuration as above will be described. As shown in FIG. 20A, an alternating input signal Sin is applied from a terminal T101a and a terminal 101b so as to excite an surface acoustic wave. More particularly, the alternating input signal Sin is applied so that a first voltage relation between the first interdigital transducer CE101 and the second interdigital transducer CE102 is in-phase with a second voltage relation between the third interdigital transducer CE103 and the fourth interdigital transducer CE104. Accordingly, the piezoelectric substrate SB100 oscillates so that a displacement distribution is in a mode S0, thereby generating a resonance signal Sout (S0) corresponding to the mode S0 and having a first frequency. The resonance signal Sout (S0) is thus taken out from a detector (not shown) such as a current-voltage conversion circuit coupled to the terminals T101a and T101b. FIG. 20A shows a case where a voltage of the terminal T101a is positive while a voltage of the terminal T101b is negative.
In contrast to the above, as shown in FIG. 20B, in a case where the alternating input signal Sin is applied so that the first voltage relation and the second voltage relation are in reverse phase, the piezoelectric substrate SB100 oscillates so that the displacement distribution is in a mode A0. As a result, a resonance signal Sout corresponding to the mode A0 and having a second frequency that is higher than the first frequency is generated, thereby a resonance signal Sout (A0) is taken out.
However, in the method to use the surface acoustic wave element SD100 in related art described as above, only two resonance signals that are the resonance signal Sout having the first frequency corresponding to the mode S0, and the resonance signal Sout having the second frequency corresponding to the mode A0 are taken out. Therefore, resonance signals having other frequencies cannot be taken out.